Nouns ending in -teur are usually masculine, but la puanteur is feminine.
Puanteur is one of the rare exceptions: learn it as it is.
Is puanteur masculine or feminine?
lapuanteurexception
The rule behind it
95.8% of -teur nouns are masculine
In context
La puanteur provenant des déchets était accablante.
The stink from the garbage was overwhelming.
Quelle puanteur ! Tu fais cuire du chou-fleur ?
What a stench! Are you cooking some cauliflower?
Pincez-vous le nez pour ne pas sentir la puanteur.
Hold your nose so you don't smell the stench.